A power transmission mechanism (1) includes a worm gear mechanism (27) including a worm wheel (11) and a worm gear (9b) a shaft (9) extending in a vertical direction and having the worm gear (9b) in a lower part a first gear (7) located in an upper direction of the shaft (9) and a second gear (5a) configured to be able to engage with the first gear (7) and connect to a shaft of a prime mover (103).
